Magazine article Science News

Recycled Crust Hails a Glittering Taxi

Magazine article Science News

Recycled Crust Hails a Glittering Taxi

Article excerpt

The ride dragged on for millions of years. But when the passenger finally arrived, it was in high style, ensconced in the heart of a diamond.

This first-class voyager was a speck of continental crust that traveled deep into the fiery innards of Earth and then made a return trip to the surface inside a South African diamond. The discovery of this unusual occupant provides the best evidence yet that continental rock gets recycled into the planet's interior, according to a report in the Jan. 11 Nature by Leon R.M.

Daniels of the University of Cape Town in South Africa and his coworkers.

Geophysicists know that Earth's dense oceanic crust can sink into the mantle through a process called subduction. They have long suspected that subduction also carries pieces of the continents into the mantle. Until now, though, they have lacked definitive evidence.

Diamonds form in the mantle at depths of more than 120 kilometers, where intense pressure squeezes carbon atoms into their most compact form. …

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